1Leaves of mature plants bipinnate
1'Leaves apparently simple, being modified to phyllodes by flattening of petiole and rachis
2Stipules spinescent
2'Stipules not spinescent
3Flowers in spikes. Pod slightly winged along the dorsal suture (Australia: Queensland, Northern Territory)
3'Flowers in glomerules
4Involucel of bracts just below the glomerule and usually hidden by the lower flowers. Pods ± circular in transverse section
4'Involucel of bracts at or below the middle of the peduncle. Pods flattened.
5Leaflets with lateral veins invisible
5'Leaflets with prominulous lateral veins beneath. Flowering glomerules light yellow to cream
6Young branches finely pubescent, glabrescent. Flowering glomerules bright yellow. Pods ± moniliform (India)
6'Young branches densely yellow pubescent. Flowering glomerules yellowish white. Pods linear-falcate, not constricted between the seeds
7Internodes armed with prickles
7'Internodes unarmed
8Prickles paired, just below the stipules (India)
8'Prickles in five rows along the internodes
9Flowers in spikes. Stems ferrugineously hispid
9'Flowers in pedunculate glomerules. Stems not hispid
10Main vein of leaflets starting and running at or about the middle of the leaflet
10'Main vein of leaflets starting at or about the margin, up to ¼ of the width of the leaflet at the acroscopic side
11Lateral veins of leaflets forming a reticulate pattern beneath, i.e. at least with distinct anastomoses close to the basiscopic margin (but see 9. A. megaladena)
11'Lateral veins of leaflets not forming a reticulate pattern beneath
12Leaflets membranous, usually with a wrinkled appearance when dry. Pod fleshy or fleshy-chartaceous, usually with wrinkled surfaces, breaking in one-seeded segments, or splitting along both sutures but then the valves held together by the internal septae
12'Leaflets chartaceous, without a wrinkled appearance when dry. Pods chartaceous, not segmented internally
13Petiolar gland at or slightly above or below the middle of the petiole
13'Petiolar gland just above the basal pulvinus
14Young stems often with a bluish waxy bloom. Lateral veins of leaflets usually distinctly reticulate. Pod 3.4-5 cm wide with prominulous veins across the seeds
14'Young stems without a bluish waxy bloom. Lateral veins of leaflets usually not reticulate, rarely anastomosing close to the basiscopic margin. Pod 2.1-2.7 cm wide, with inconspicuous veins
15Leaflets shortly petiolulate; petiolules 0.2-0.4 mm; main vein starting at about ¼ of the width of the leaflet at the acroscopic margin and running ± parallel to the acroscopic margin
15'Leaflets sessile; main vein starting at the acroscopic margin, but not running parallel to the acroscopic margin
16Ultimate parts of branches densely red-brown glandular puberulous with distinct alternating light brown and dark brown lines. Calyx narrowly campanulate, 1.6-2 mm long, eglandular. Stamens 2.8-3.5 mm
16'Ultimate parts of branches with yellowish glandular hairs, without distinct longitudinal lines. Calyx broadly cup-shaped to campanulate, 2-2,3 mm, with light-yellowish glands. Stamens 6.5 mm
17Petiolar and rachis glands stipitate or obconical; rachis glands numerous, usually at the junction of all pairs of pinnae, occasionally absent at the proximal 2 pairs.
17'Petiolar and rachis glands sessile, circular-elliptic, patelliform, or saddle-shaped; rachis glands not numerous, usually present at the junction of the 1-5 distal pairs of pinnae only
18Young branches with a dense cover of blackish glandular hairs. Main vein of leaflets running diagonally. Glomerules of flowers 7-8 mm in diameter; floral bracts lance- olate-spathulate. Pod chartaceous, continuous within, gradually narrowing into the stalk
18'Young branches with a ± dense cover of reddish glandular hairs. Main vein of leaflets running parallel to the acroscopic margin for at least ¼ of its length. Floral bracts ovate-oblong to obovate-oblong, or oblong-spathulate. Pod, where known, thinly woody, discontinuous within, seeds each in a separate compartment, abruptly narrowed into the stalk
19Ultimate parts of branches without or with very few scattered non-glandular hairs. Glomerules of flowers c. 10-11 mm in diameter.
19'Ultimate parts of branches patently puberulous, setose or shortly fulvous tomentose to velutinous by non-glandular hairs
20Ultimate parts of branches shortly fulvous tomentose to velutinous and with scattered, sessile, glandular hairs. Glomerules (7-)9-10 mm in diameter
20'Ultimate parts of branches patently puberulous to setose and with a dense cover of reddish, sessile, glandular hairs
21Stipules triangular, acute, c. 0.5-0.8 by 0.3-0.7 mm. Pinnae with up to 40 pairs of leaflets; leaflets angled to auriculate at the base, apex bent acroscopically. Glomerules c. 6 mm in diameter; calyx dotted by minute glands
21'Stipules ovate-lanceolate or lanceolate-falcate, c. 1.2-3 by 0.4-0.7 mm. Pinnae with up to 63 pairs of leaflets; leaflets asymmetrically truncate at the base, apex more or less straight. Glomerules 6.5-7.5 mm in diameter; calyx eglandular
22Petiolar gland at or above the middle of the petiole
22'Petiolar gland well below the middle of the petiole, usually placed in the lower fifth just above the basal pulvinus
23Leaflets 1-1.5 mm wide, lateral veins prominuous to raised
23'Leaflets 0.3-0.8 mm wide, lateral veins prominuous to inconspicuous
24Apex of leaflets obtuse; lateral veins visible but hardly raised. Ovary glabrous. Pod with a narrow wing
24'Apex of leaflets acute; lateral veins invisible to hardly visible. Ovary villous. Pod unwinged
25Leaf-rachis and pinnae without extrafloral nectaries. Flowers pedicellate (W Indies)
25'Leaf-rachis with extrafloral nectaries. Flowers sessile (Australia)
26Pinnae usually (5-)7-20 pairs; leaflets 20-50 pairs per pinna in well-developed leaves (if overlapping then keyed under both leads)
26'Pinnae number variable; if pinnae 3-5 pairs, then leaflets 15-20 pairs per pinna
27Branchlets acutely angular, glabrous; leaflets widely spaced, 5-10 mm (Australia: New South Wales, Victoria)
27'Branchlets not acute angular, puberulous; leaflets crowded, 2-4 mm
28Pinnae 6-10 pairs; leaflets 18-30 pairs per pinna; puberulous on both surfaces (Australia: Queensland, New South Wales)
28'Pinnae 7-20 pairs; leaflets 20-50 pairs per pinna, usually glabrous above.
29Glands present between the rachis nodes; leaflets 1.8-2.2(-2.5) mm, apex rounded. Pod c. 6 mm wide, puberulous, glabrescent, not glaucous (Australia: New South Wales, Victoria)
29'Leaf-rachis internodes eglandular; leaflets (2-)2.6-3.5 mm, apex often subacute. Pod 7-9(-12) mm wide, glabrous, usually glaucous (Australia: New South Wales, Victoria, Tasmania)
30Larger leaflets 20-50 mm long (Australia: New South Wales)
30'Leaflets all or for the greater part shorter than 20 mm
31Glands present between the rachis nodes; leaf-rachis with appressed indumentum (Australia: Queensland, New South Wales)
31'Leaf-rachis internodes eglandular; leaf rachises either with patent indumentum or glabrous
32Branchlets and leaf-rachises with patent indumentum (glabrescent in the Australian species A. spectabilis A. Cunn. ex Benth.)
32'Branchlets and leaf-rachises glabrous
33Leaflets 12-15 pairs per pinna (Australia: New South Wales)
33'Leaflets 4-6(-10) pairs per pinna
34Pinnae 2-3(-4) pairs; rachis 0.4-1.5 cm long; leaflets 4-8 by (1.5-)2-3 mm (Australia: Queensland, New South Wales)
34'Pinnae 3-5(-7) pairs; rachis 2-7(-9.5) cm long; leaflets 6—11(—13) by 2.5-5 mm (Australia: Queensland, New South Wales)
35Leaflets 10-15 pairs per pinna
35'Leaflets 4-6(-10) pairs per pinna
36Leaves subsessile; leaflets 3-8 mm. Pod 0.9-1.2 cm wide (Australia: New South Wales)
36'Leaves petioled; leaflets 9-17 mm. Pod 0.7 cm wide (Australia: Queensland, New South Wales)
37Pinnae 2-3(-4) pairs; rachis 0.4-1.5 cm long; leaflets 4-8 by (1.5-)2-3 mm (Australia: Queensland, New South Wales)
37'Pinnae 3-5(-7) pairs; rachis 2-7(-9.5) cm long; leaflets 6—11(—13) by 2.5-5 mm (Australia: Queensland, New South Wales).
38Flowers in spikes
38'Flowers in glomerules
39Phyllodes completely covered with appressed silvery grey pubescence (Australia: Queensland)
39'Phyllodes without silvery grey pubescence
40Flowers all or for the greater part tetramerous. Pods linear, straight to curved, 0.3-0.6 cm wide
40'Flowers pentamerous
41Foliar gland not prominent. Phyllodes straight, 5-10 by (0.2-)0.4-l cm. Spikes sparsiflorous. Pod c. 13 by 0.3 cm (Australia: Queensland, New South Wales, Victoria)
41'Foliar gland prominent. Phyllodes variable, 4-16 by 0.3-2.5 cm. Spikes loose and interrupted. Pod 2.5-15 by 0.3-2.5 cm (Australia: extratropical areas of E Australia, Tasmania)
42Phyllodes without anastomosing secondary longitudinal veins
42'Phyllodes at least with a few anastomosing secondary longitudinal veins
43Spikes sessile with hirsute rachis. Pods papery, c. 1 cm wide
43'Spikes shortly pediculate, not hirsute. Pods coriaceous to woody
44Pulvinus (4-)5-20 mm long; phyllodes with yellowish veins and margin. Pods woody, obovoid-oblong, with transverse but hardly reticulate veins, 5 by 2-3.5 cm
44'Pulvinus 4-7 mm long; phyllodes without yellowish veins and margins. Pods coriaceous to subwoody, with transverse anastomosing veins, oblong, 8 by (l-)2 cm
45Spikes on peduncles 0.5-1 cm long. Phyllodes 9-22 times as long as wide
45'Spikes on peduncles up to 0.5 cm long. Phyllodes often less than 20 times as long as wide
46Branchlets with indumentum of appressed hairs (Australia: Queensland)
46'Branchlets scurfy or glabrous
47Branchlets stout and acutely angular. Phyllodes with 3-5 prominent longitudinal veins running from the base, and with secondary veins forming a fine reticulum. Pods linear, coiled and turgid. Flowers rusty, cream, greenish, or pale yellow
47'Branchlets slender, not acutely angular. Flowers, where known, bright golden yellow
48Secondary veins of phyllodes forming a delicate reticulum; phyllodes rather short, 5-12 by 1.4-3.2 cm
48'Secondary veins with spaced anastomoses; phyllodes longer, 10-21(-26) by 1-2.6(-3) cm
49Pods contorted with transversely placed seeds. Pulvinus 4-6 mm long; phyllodes with 3 or 4, not yellowish, longitudinal veins. Spikes somewhat interrupted
49'Pods linear, somewhat coiled, with longitudinal placed seeds. Pulvinus (3-)5-10 mm long; phyllodes with 3 yellowish, longitudinal veins. Spikes moderately dense
50Phyllodes flat with one longitudinal vein, occasionally with a second longitudinal vein developed (Australia)
50'Phyllodes flat, with three or more longitudinal main veins
51Glomerules axillary, arranged in very short racemes, less than 15 mm long, before development never enclosed by imbricate scarious bracts. Phyllodes with one longitudinal main vein and along this a much weaker and shorter vein (Australia)
51'Glomerules arranged in racemes or panicles; if glomerules less than 15 mm long, then enclosed by imbricate bracts before development. Phyllodes with a single main vein
52Phyllodes less than 3 times as long as wide, with an apical point
52'Phyllodes more than 3 times as long as wide
53Branchlets patently grey-hairy. Phyllodes elliptic, slightly lop-sided, the larger ones 2.5-5 by 1-2.5 cm, conspicuously glaucous on both surfaces, grey-hairy (Australia)
53'Branchlets glabrous. Phyllodes deltoid or semi-orbicular, very unequal-sided, broader on the distal side, glabrous; 0.8-2.5 by 0.5-2 cm (Australia)
54Phyllodes all or nearly all less than 1.3 cm wide; branchlets conspicuously angular
54'Phyllodes 1.3-3 cm wide
55Larger phyllodes longer than 5 cm
55'Larger phyllodes 2-4 by 0.2-0.3 cm (Australia)
56Branchlets much flattened at the top, angular downwards. Glomerules with less than 15 flowers; racemes 1-2 cm long, enclosed by rather large, striate bracts (Australia)
56'Branchlets trigonous at the apex, the older ones ribbed. Glomerules 30-50-flowered; racemes 1.5-5 cm long, without bracts (Australia)
57Branchlets at the top angularly ribbed. Phyllodes straight to slightly curved, 8-12 by 0.7-0.8 cm. Glomerules 20-30-flowered, less than 1 cm in diameter (Australia)
57'Branchlets subterete. Phyllodes lanceolate-falcate, with apex obtuse, 7.5-15 cm long. Glomerules 50-100-flowered, more than 1 cm in diameter (Australia)